From b2fc1fb4a13ffa58640333a3909dd0e53bd21995 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 31 May 2017 16:29:33 +0200
Subject: Adjust extension semantics in file rule to match
 search_existing_file()

---
 build2/rule.cxx   |  7 ++++++-
 build2/search.cxx |  2 +-
 build2/target.cxx | 13 +++++++++----
 build2/target.hxx | 36 ++++++++++++++++++++++++------------
 4 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/build2/rule.cxx b/build2/rule.cxx
index a462e58..a48fef2 100644
--- a/build2/rule.cxx
+++ b/build2/rule.cxx
@@ -67,7 +67,12 @@ namespace build2
             // derivation function to treat this as prerequisite (just like
             // in search_existing_file()).
             //
-            pt.derive_extension (nullptr, true);
+            if (pt.derive_extension (true) == nullptr)
+            {
+              l4 ([&]{trace << "no default extension for target " << pt;});
+              return false;
+            }
+
             p = &pt.derive_path ();
           }
 
diff --git a/build2/search.cxx b/build2/search.cxx
index 6be62b2..66f13a9 100644
--- a/build2/search.cxx
+++ b/build2/search.cxx
@@ -105,7 +105,7 @@ namespace build2
         // (of course, if the user specified the extension explicitly, we will
         // still do so).
         //
-        l4 ([&]{trace << "no existing file for prerequisite " << cpk;});
+        l4 ([&]{trace << "no default extension for prerequisite " << cpk;});
         return nullptr;
       }
     }
diff --git a/build2/target.cxx b/build2/target.cxx
index 1b6757c..3ee9850 100644
--- a/build2/target.cxx
+++ b/build2/target.cxx
@@ -530,8 +530,8 @@ namespace build2
 
   // path_target
   //
-  const string& path_target::
-  derive_extension (const char* de, bool search)
+  const string* path_target::
+  derive_extension (bool search, const char* de)
   {
     // See also search_existing_file() if updating anything here.
     //
@@ -541,7 +541,7 @@ namespace build2
       // Note that returning by reference is now MT-safe since once the
       // extension is specified, it is immutable.
       //
-      return *p;
+      return p;
     else
     {
       optional<string> e;
@@ -559,10 +559,15 @@ namespace build2
         if (de != nullptr)
           e = de;
         else
+        {
+          if (search)
+            return nullptr;
+
           fail << "no default extension for target " << *this;
+        }
       }
 
-      return ext (move (*e));
+      return &ext (move (*e));
     }
   }
 
diff --git a/build2/target.hxx b/build2/target.hxx
index 884b185..19c8946 100644
--- a/build2/target.hxx
+++ b/build2/target.hxx
@@ -1190,19 +1190,22 @@ namespace build2
 
     // As above but ignore the extension.
     //
+    const target*
+    find (const target_type& type,
+          const dir_path& dir,
+          const dir_path& out,
+          const string& name) const
+    {
+      slock l (mutex_);
+      auto i (map_.find (target_key {&type, &dir, &out, &name, nullopt}));
+      return i != map_.end () ? i->second.get () : nullptr;
+    }
+
     template <typename T>
     const T*
     find (const dir_path& dir, const dir_path& out, const string& name) const
     {
-      slock l (mutex_);
-
-      auto i (
-        map_.find (
-          target_key {&T::static_type, &dir, &out, &name, nullopt}));
-
-      return i != map_.end ()
-        ? static_cast<const T*> (i->second.get ())
-        : nullptr;
+      return static_cast<const T*> (find (T::static_type, dir, out, name));
     }
 
     // If the target was inserted, keep the map exclusive-locked and return
@@ -1424,11 +1427,20 @@ namespace build2
     derive_path (path_type base, const char* default_ext = nullptr);
 
     // As above but only derives (and returns) the extension (empty means no
-    // extension used). If search is true then look for the extension as if
-    // it was a prerequisite, not a target.
+    // extension used).
     //
     const string&
-    derive_extension (const char* default_ext = nullptr, bool search = false);
+    derive_extension (const char* default_ext = nullptr)
+    {
+      return *derive_extension (false, default_ext);
+    }
+
+    // As above but if search is true then look for the extension as if it was
+    // a prerequisite, not a target. In this case, if no extension can be
+    // derived, return NULL instead of failing (like search_existing_file()).
+    //
+    const string*
+    derive_extension (bool search, const char* default_ext = nullptr);
 
     // Const versions of the above that can be used on unlocked targets. Note
     // that here we don't allow providing any defaults since you probably
-- 
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